This invention relates to a perforating machine. More particularly, this invention relates to a machine for perforating a continuous web of material at variable points. Still more particularly, this invention relates to a machine capable of perforating or cutting a moving web of material at predetermined points.
As is known, various machines have been provided for the perforating of continuous webs of foam material. For example, machines have been known in which a web of foam material is conveyed through a perforating station in which a rotating roll having a perforating bar thereon is caused to impart a transverse line of perforations in the web on each cycle of the roll. Generally, the perforating roll is combined with a guide roll to form a nip through which the web material is conveyed and against which the perforating bar may react in order to perform a perforating operation. One of the problems which arises with such a machine occurs when the foam material is relatively thin as any differential in speed between the speed of the perforating bar and the speed of the web may cause a tearing of the web during the time of contact between the perforating bar and the web. Thus, in such cases, the speed of the perforating roll and guide roll must be matched to the speed of the web. Another disadvantage is that it is very difficult to change the center line to center line distance between successive lines of perforations should a need arise to change the length of the xe2x80x9cpanelxe2x80x9d formed between pairs of successive lines of perforations. Generally, attempts are made to change the speed of the perforating roll or to change the speed of the web in order to vary the longitudinal distance between transverse lines of perforations in the web. However, this increases the risk that a web may be torn during the perforating operation due to a difference in speed between the perforating roll and the web.
Other machines have also been known which are of the start/stop type. However, such machines are subject to continuous wear because of the start/stop operation and take longer to make perforations.
Accordingly, it is an object of the invention to provide a machine capable of perforating a moving web of material on the fly without tearing of the web.
It is another object of the-invention to provide a machine in which a web of material moving at a constant speed can be perforated in a variable manner.
It is another object of the invention to provide a perforating machine for a web of material which can be adjusted during operation.
It is another object of the invention to provide a machine which is capable of perforating webs of material of relatively thin thickness.
It is another object of the invention to provide a machine which is capable of perforating, slitting and/or sheeting a traveling web of foam or plastic material in a continuous operation.
It is another object of the invention to be able to cut a traveling web of foam or plastic material into one or more streams of small panels of accurate size.
Briefly, the invention provides a perforating machine which includes a supply station for receiving web of material, conveying means for conveying the web of material from the supply station, a perforating station for perforating the conveyed web at spaced apart distances to define parallel spaced apart lines of weakening in the web for subsequent separation of the web into separate sheets and a receiving station for receiving the perforated web of material from the perforating station.
In one embodiment of the invention, the perforating station includes a base roll for supporting the conveyed web during passage through the perforating station and means for selectively moving the base roll between a retracted position and a raised position. The perforating station also includes a perforator roll opposite the base roll for imparting at least a transversely disposed line of perforations in the web passing between the rolls with the base roll in the raised position.
Basically, the machine is constructed in this embodiment to perforate a moving web of material, such as a plastic foam web, a plastic bubble web of single or multi-ply construction, and the like, with spaced apart lines of perforations and is constructed so that the spacing of the lines of perforations can be varied when desired.
During use, the conveying means conveys the web between the two rolls of the perforating station. In this regard, the perforator roll carries a perforating bar of suitable construction for perforating the web of material on the fly. During operation, the perforating roller remains on a fixed axis while rotating. The opposed base roll, on the other hand, is disposed in spaced relation below the perforating roller in a retracted position. When a perforation is to take place, the base roll is moved upwardly into the raised position. After a perforation has occurred, the base roll is returned to the retracted position. In this regard, the machine is further provided with a timing means for adjustably timing the actuation of the means for moving the lower base roll into the raised position so that a perforation can be effected in the moving web.
The timing means may employ a cam mounted on the perforator roll in a position indicative of the position of the perforating bar for rotation with the perforating roll. In addition, a first switch is mounted in a fixed position in the perforating station for emitting a signal during passage of the cam thereby while a second switch is mounted in a further fixed position in the perforating station for emitting a second signal during passage of the cam thereby. In addition, a programmer is provided for receiving the signals from the two switches for actuating the means for moving the lower roll in response to a predetermined sequence of the signals. For example, when the cam passes by the first switch, a signal is emitted to indicate the position of the perforating bar on the perforating roll. When the second limit switch is activated, a second signal is emitted so as to cause lifting of the lower roll into the raised position. As the perforating roll continues to rotate, the perforating bar forms a perforation in the moving web. As the perforating roll makes a second revolution, the first switch emits a further signal (i.e. a third signal) indicating that a perforation has been made. Activation of the second switch causes a further signal (i.e. a fourth signal) to be emitted to cause the lower roller to be retracted into the retracted position so that no perforation can occur. This sequence of signals can then be repeated such that a perforation is made for every two revolutions of the perforating roll.
By adjusting the sequence of signals, the spacing between successive lines of perforations can be varied in a multiple or fractional relationship. For example, if the above exemplified sequence of four signals produces perforations on a twelve inch spacing, a sequence of only two of the signals would produce a spacing of six inches whereas a sequence of six signals would provide spacings of eighteen inches.
The machine is also provided with a transmission for rotating the perforator roll in a cycle having an acceleration phase which occurs during the perforation of the web and a deceleration phase which occurs after perforation of the web. In this way, the speed of the perforating bar can be adjusted to match the conveying speed of the web in order to avoid tearing of the web. Thus, the rotational speed of the perforating roll can be quite different from the conveying speed of the web since the perforating roll can be accelerated to a suitable speed to match with the speed of the web at the time of perforation.
In order to handle foam materials in a gentle manner, the lower base roll of the perforating station is made with a relatively soft surface. For example, the roll may be in the form of a brush roll having a plurality of upstanding filaments for supporting the conveyed web of material. In addition, the brush roll may be rotated by suitable means during conveyance of the web, particularly in the case of relatively thin foam materials.
The machine is particularly suitable for perforating foam webs having thicknesses of from {fraction (1/32)} to xc2xc inches.
The machine may also be provided with at least one slitter upstream of the perforator roll for impressing a longitudinal line of weakening in the conveyed web. In this way, the web may be separated into two or more sections. Additional slitters may also be provided for trimming the edges of the web or for effecting additional longitudinal lines of weakening to form multiple rolls of perforated web or multiple panels.
The perforating roll may also be provided with a bar which effects a complete severance of the web rather than simply effecting a line of perforations in the web. In this embodiment, successive panels can be cut from the traveling web in a xe2x80x9csheetingxe2x80x9d manner. The resulting panels can then be stacked in a suitable manner in the receiving station.